fix(context_meter): satisfy pyright narrowing in _tools_cache_key

pyright doesn't narrow across two separate t.get("parameters") calls, so it
flagged .keys() as reachable when t.get("parameters") is None even though
the isinstance(..., dict) guard makes that unreachable at runtime. Binds
t.get("parameters") to a local once and isinstance-checks that — a real (if
narrow) robustness improvement too, since it drops a redundant second dict
lookup. No behavior change; confirmed via `pyright orchestrator/context_meter.py`
-> 0 errors, and tests/test_context_meter.py + tests/test_compaction.py still
green.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: AdamMagued

orchestrator/context_meter.py

@@ -274,12 +274,15 @@ def _tools_cache_key(tools: list[dict]) -> tuple:
     name) without paying for a full JSON serialization on every call.
     """
     try:
+        def _param_keys(tool: dict) -> tuple | None:
+            params = tool.get("parameters")
+            return tuple(sorted(params.keys())) if isinstance(params, dict) else None
+
         return tuple(
             (
                 t.get("name"),
                 len(str(t.get("description") or "")),
-                tuple(sorted(t.get("parameters").keys()))
-                if isinstance(t.get("parameters"), dict) else None,
+                _param_keys(t),
             )
             for t in tools
         )